For some reason, certain cab drivers do not allow pets in their cars. Because pets can be messy. If a dog who is not used to travelling might pee, which would cost hundreds of dollars to the driver in cleanup fees. It’s also difficult to get the smell out of the seats, and of course the hairs.
Whether you are a pet lover or not, but the pet hairs will be visible in a car with a darker interior which would look odd to other riders. Another reason is that some drivers are allergic to pets and you have to take care of this.